U.S. patent number 7,501,913 [Application Number 11/675,141] was granted by the patent office on 2009-03-10 for power line communication apparatus and connecting device.
This patent grant is currently assigned to Panasonic Corporation. Invention is credited to Tsunehiro Hanada, Yuji Igata, Akihiro Yamashita.
United States Patent |
7,501,913 |
Hanada , et al. |
March 10, 2009 |
Power line communication apparatus and connecting device
Abstract
A cable connecting device for power line communication includes:
a first wiring line 231 and a second wiring line 232 through which
AC power is capable of being supplied; a power plug 120 which is
electrically connected to the first wiring line 231 and the second
wiring line 232 and whose wiring lines are capable of being
supplied with AC power; an Ethernet port 110 through which a
communication signal is capable of being input and output; a power
line communication modem 220 that is connected to the Ethernet port
110 and that is connected to the second wiring line 232 through
which a communication signal is transmitted by using AC power input
to the power plug 120 through the first wiring line 231 between the
power plug 120 and the Ethernet port 110; a filter 210 disposed on
the first wiring line 231 and having high impedance in at least a
frequency band used for power line communication rather than a
frequency band used for AC power; and connectors 101 to 104 which
axe electrically connected to the first wiring line 231 between the
filter 210 and the power line communication modem 220 and to which
AC power from the first wiring line 231 is capable of being
supplied.
Inventors: |
Hanada; Tsunehiro (Fukuoka,
JP), Yamashita; Akihiro (Saga, JP), Igata;
Yuji (Fukuoka, JP) |
Assignee: |
Panasonic Corporation (Osaka,
JP)
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Family
ID: |
38369202 |
Appl.
No.: |
11/675,141 |
Filed: |
February 15, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20070190840 A1 |
Aug 16, 2007 |
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Foreign Application Priority Data
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Feb 15, 2006 [JP] |
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2006-038319 |
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Current U.S.
Class: |
333/132;
375/259 |
Current CPC
Class: |
H01R
13/70 (20130101); H01R 13/719 (20130101); H01R
25/003 (20130101); H04L 12/10 (20130101); H01R
13/6666 (20130101) |
Current International
Class: |
H03H
7/46 (20060101) |
Field of
Search: |
;333/132
;340/310.01,310.07,310.08 ;375/259 ;307/40 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
English translation of JPH08-032495A. cited by other.
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Primary Examiner: Chang; Daniel D
Attorney, Agent or Firm: Dickinson Wright, PLLC
Claims
The invention claimed is:
1. A power line communication apparatus that superimposes a signal
having a first frequency on power having a second frequency lower
than the first frequency, comprising: a first connector to which
the power is input; a communication circuit that superimposes the
signal on the power input to the first connector; a power supply
circuit that supplies the power input to the first connector to the
communication circuit; a second connector that outputs the power
input to the first connector to the outside of the power line
communication apparatus; and a single filter that has impedance
characteristics in which impedance corresponding to the first
frequency is higher than impedance corresponding to the second
frequency, wherein the first connector is connected to the power
supply circuit through the single filter, and the first connector
is connected to the second connector through the single filter.
2. The power line communication apparatus according to claim 1,
wherein the communication circuit is connected to the first
connector through a first line and transmits the signal onto the
first line, the power supply circuit is connected to the first
connector through a second line and supplies the power input to the
first connector to the communication circuit through the second
line, the single filter is provided on the second line between the
first connector and the power supply circuit, and the second
connector is provided on the second line between the single filter
and the power supply circuit.
3. The power line communication apparatus according to claim 2,
further comprising: a selector that disconnects the second
connector from the second line and connects the second connector to
the first line.
4. The power line communication apparatus according to claim 1,
further comprising: a surge absorber that is provided between the
second connector and the single filter so as to absorb surge.
5. The power line communication apparatus according to claim 4,
wherein the second line has a connection point to which the second
connector is connected, and the surge absorber is provided between
the single filter and the connection point.
6. The power line communication apparatus according to claim 1,
wherein the single filter is connected to the first connector
through a line including an approach path and a return path and has
passive elements on the approach path and the return path.
7. The power line communication apparatus according to claim 6,
wherein the passive elements have substantially the same
characteristic values.
8. The power line communication apparatus according to claim 6,
wherein the passive elements are inductors.
9. The power line communication apparatus according to claim 8,
wherein the passive elements are configured to include only
inductors.
10. The power line communication apparatus according to claim 1,
wherein the first frequency is in a megahertz band.
11. The power line communication apparatus according to claim 10,
wherein the megahertz band is 1.705 MHz to 80 MHz.
12. The power line communication apparatus according to claim 1,
wherein the second frequency is 60 Hz.
13. The power line communication apparatus according to claim 1,
wherein the first connector is a plug.
14. The power line communication apparatus according to claim 1,
wherein the power supply circuit converts AC components of the
power to DC components and supplies the converted power to the
communication circuit.
15. The power line communication apparatus according to claim 14,
wherein the power supply circuit converts the AC components of the
power to the DC components by using a switching element.
16. The power line communication apparatus according to claim 1,
wherein the second connector is an outlet.
17. The power line communication apparatus according to claim 16,
wherein a plurality of the outlets are provided.
18. A connecting device for a power line communication apparatus
that superimposes a signal having a first frequency on power having
a second frequency lower than the first frequency, comprising: a
first connector to which the power is input; a power supply circuit
that supplies the power input to the first connector to a
communication circuit that superimposes the signal on the power; a
second connector that outputs the power input to the first
connector to the outside of the power line communication apparatus;
and a single filter has impedance characteristics in which
impedance corresponding to the first frequency is higher than
impedance corresponding to the second frequency, wherein the first
connector is connected to the power supply circuit through the
single filter, and the first connector is connected to the second
connector through the single filter.
Description
BACKGROUND
The present invention relates to a power line communication
apparatus and a connecting device used in power line
communication.
In known power line communication using the spread spectrum
communication technology disclosed in, for example, JP-A-8-32495,
there is used a cable connecting device for power line
communication having a spread spectrum communication circuit, which
includes a modulation unit and a power connector for connecting a
non-power line communication apparatus that does not perform power
line communication. Further, a power strip provided with a
plurality of outlets is disclosed U.S. Pat. No. 6,956,464B2.
However, in the cable connecting device for power line
communication or the power strip, a power filter for modem is
required in addition to a power filter for connector. Accordingly,
there has been a problem in which the filters are separately
provided.
SUMMARY
The invention has been finalized in view of the drawbacks inherent
in the related art. In the invention, since a power supply circuit
and a second connector are connected to a first connector through
the same filter, the filter can have both a function as a filter
for the power supply circuit and a function as a filter for
electrical equipment connected to the second connector. As a
result, it is not necessary to separately prepare a filter for a
power supply circuit and a filter for electrical equipment
connected to the second connector. Thus, it is an object of the
invention to provide a power line communication apparatus and a
connecting device capable of efficiently using a filter.
In order to achieve the above object, according to an aspect of the
invention, a power line communication apparatus that superimposes a
signal having a first frequency on power having a second frequency
lower than the first frequency includes: a first connector to which
the power is input; a communication circuit that superimposes the
signal on the power input to the first connector; a power supply
circuit that supplies the power input to the first connector to the
communication circuit; a second connector that outputs the power
input to the first connector to the outside of the power line
communication apparatus; and a single filter that has impedance
characteristics in which impedance corresponding to the first
frequency is higher than impedance corresponding to the second
frequency, wherein the first connector is connected to the power
supply circuit through the single filter, and the first connector
is connected to the second connector through the single filter,
In the configuration described above, since the power supply
circuit and the second connector are connected to the first
connector through a single filter, the filter can have both a
function as a filter for the power supply circuit and a function as
a filter for electrical equipment connected to the second
connector. Accordingly, since a filter can be efficiently used,
duplication of filters can be prevented.
Further, in order to achieve the object, according to another
aspect of the invention, a connecting device for a power line
communication apparatus that superimposes a signal having a first
frequency on power having a second frequency lower than the first
frequency includes: a first connector to which the power is input;
a power supply circuit that supplies the power input to the first
connector to a communication circuit that superimposes the signal
on the power; a second connector that outputs the power input to
the first connector to the outside of the power line communication
apparatus; and a single filter that has impedance characteristics
in which impedance corresponding to the first frequency is higher
than impedance corresponding to the second frequency, wherein the
first connector is connected to the power supply circuit through
the single filter, and the first connector is connected to the
second connector through the single filter.
In the configuration described above, since the power supply
circuit and the second connector are connected to the first
connector through a single filter, the filter can have both a
function as a filter for the power supply circuit and a function as
a filter for electrical equipment connected to the second
connector. Accordingly, since a filter can be efficiently used,
duplication of filters can be prevented.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a view schematically illustrating a cable connecting
device for power line communication in a first embodiment.
FIG. 2 is a circuit diagram illustrating the cable connecting
device for power line communication in the first embodiment.
FIG. 3 is a circuit diagram illustrating a cable connecting device
for power line communication in a second embodiment.
FIG. 4 is a block diagram illustrating a circuit of a power line
communication modem in the first embodiment.
FIG. 5 is an equivalent circuit diagram when a power connector is
connected to a power line in the first embodiment with a known
unbalanced filter interposed therebetween.
FIG. 6 is an equivalent circuit diagram when a power connector is
connected to the power line in the first embodiment with a balanced
filter interposed therebetween.
FIG. 7A is a view illustrating gain-frequency characteristic when
an unbalanced filter and a balanced filter in the first embodiment
are formed by using a constant K filter having characteristic
impedance of 100 .OMEGA. and a cutoff frequency of 50 KHz.
FIG. 7B is a view illustrating impedance-frequency characteristic
when an unbalanced filter and a balanced filter in the first
embodiment are formed by using a constant K filter having
characteristic impedance of 100 .OMEGA. and a cutoff frequency of
50 KHz.
FIG. 8A is a circuit diagram in a case when two inductors are used
as a filter in the first embodiment.
FIG. 8B is a circuit diagram in a case when two inductors are
magnetically coupled to form a filter in the first embodiment in
order to improve impedance.
DETAILED DESCRIPTION
Hereinafter, a power line communication apparatus and a connecting
device according to embodiments of the invention will be described
with reference to accompanying drawings.
First Embodiment
First, a cable connecting device for power line communication
according to an embodiment of the invention will be schematically
described.
As shown in FIG. 1, a cable connecting device for power line
communication 100 has connectors 101, 102, 103, and 104, an
Ethernet (Registered Trademark) port 110 to which an Ethernet cable
is connectable, a power plug 120, and a selection switch 130. Here,
the connectors 101, 102, 103, and 104 are examples of a second
connector. Here, only explanation related to a first embodiment
will be made.
In addition, as an example of the cable connecting device for power
line communication 100, an example in which the invention is
applied to a power strip (in other words, surge strip) is
illustrated, as shown in FIG. 1. However, the invention is not
specifically limited to the power strip but may be applied to
various products. It is not necessary that the cable connecting
device for power line communication 100 have a power cable or a
plurality of outlets like the power strip described above. For
example, the cable connecting device for power line communication
100 may be an AC adaptor having a pair of plug and outlet. In
addition, the invention may be applied to a modem. In this case, it
is preferable that the modem have at least an outlet corresponding
to one of the connectors 101, 102, 103, and 104. Moreover, the
invention may be applied to electrical equipment having a
communication function, such as so-called `networking appliances`.
In the case, in the same manner as the modem, it is preferable to
include at least an outlet.
The connectors 101, 102, 103, and 104 are connectors for supply of
power to non-power line communication apparatuses. Further, the
number of connectors is not limited to four of the connectors 101,
102, 103, and 104 but may be more than four. The non-power line
communication apparatus refers to electrical equipment, such as
home appliances, which do not perform power line communication.
Furthermore, the Ethernet port 110 is a connecting port of a cable
for input and output of a communication signal. In addition, the
power plug 120 is connected to a power supply source, such as a
wall outlet.
In addition, the selection switch 130 will be described later
because the selection switch 130 is not used in the present
embodiment.
Further, the power supply source is a commercial power supply that
supplies AC power having a voltage of AC 100 V and a power
frequency of 60 Hz; however, it is possible to commercial voltage
(for example, 120 V or 220 V) and a power frequency (for example,
50 Hz) of the AC power. Furthermore, the power plug 120 may not be
necessarily provided. For example, a power plug connected with a
power cord (so-called AC cable) may be externally provided and the
cable connecting device for power line communication 100 may have a
power plug connector, into which the externally provided power plug
is inserted, provided on a forefront stage (definition of a `front
stage` will be described later) thereof. In addition, the Ethernet
port 110 is an example of a communication connector through which a
communication signal is capable of being input and output. For
example, the Ethernet port 110 is a modular jack such as the RJ45,
but is not specifically limited thereto.
As shown in FIG. 2, in addition to the above configuration, the
cable connecting device for power line communication 100 includes a
filter 210, a power line communication modem 220, a surge absorber
230, a first wiring line 231, a second wiring line 232, a wiring
line 233 for Ethernet port, and wiring lines 241 to 244 for
connectors. In addition, the power line communication modem 220
includes a power circuit 221 and a communication circuit 222. In
addition, the first wiring line 231 is an example of a first line.
The first line may be configured in various ways, such as a wire or
a pattern on a circuit board, as long as a power plug and a
communication circuit can be electrically connected to each other.
Moreover, the second wiring line 232 is an example of a second
line. The second line may be configured in various ways, such as a
wire or a pattern on a, circuit board, as long as a power plug and
a power supply circuit can be electrically connected to each other.
The power line communication modem 220 may be provided between the
filter 210 and the connectors 101, 102 103, and 104.
The Ethernet port 110 is an example of a communication connector.
In addition, the power plug 120 is an example of a first connector.
In addition, the power line communication modem 220 is an example
of a power line communication unit. In addition the first wiring
line 231 is an example of a first line. In addition the second
wiring line 232 is an example of a second line. In FIG. 2, the same
parts as in the cable connecting device for power line
communication 100 shown in FIG. 1 are denoted by the same reference
numerals. The characteristics of the parts denoted by the same
reference numerals are as described above.
The first wiring line 231 is a power line that serves to connect
the power plug 120 and the power circuit 221 of the power line
communication modem 220 to each other and transmit power supplied
from the power plug 120 to the power circuit 221. Assuming that a
side close to the power plug 120 is a `front stage` and a side
close to the power line communication modem 220 is a `rear stage`
on the first wiring line 231, the second wiring line 232, the
filter 210, the surge absorber 230, and the wiring lines 241 to 244
for connectors are electrically connected in the order from the
front stage to the rear stage on the first wiring line 231. In this
case, the wiring lines 241 to 244 for connectors are electrical
wiring lines that serve to connect the connectors 101 to 104 and
the first wiring line 231 to each other and transmit the power
supplied from the power plug 120 to the connectors 101 to 104.
The second wiring line 232 is a communication line that serves to
connect the power plug 120 and the communication circuit 222 of the
power line communication modem 220 to each other, transmit a
communication signal, which is input to the power plug 120 from the
outside (not shown), to the communication circuit 222, and transmit
to the power plug 120 a communication signal transmitted through
the wiring line 233 for Ethernet port. Moreover, in the present
embodiment, the first wiring line 231 and the second wiring line
232 partially overlap each other at a front stage on the first
wiring line 231 positioned in front of the filter 210.
The wiring line 233 for Ethernet port serves to connect the power
line communication modem 220 and the Ethernet port 110 to each
other, transmit to the Ethernet port 110 the communication signal
transmitted through the second wiring line 232, and transmits to
the communication circuit 222 a communication signal transmitted
from an apparatus (not shown).
The filter 210 has impedance characteristics in which impedance
corresponding to a power frequency is higher than impedance
corresponding to a communication frequency As described above, the
power frequency is 60 Hz. The communication frequency refers to a
frequency used in power line communication and is in a range of
1.705 MHz to 80 MHz, for example. Therefore, the filter 210 has
impedance characteristics in which impedance corresponding to 60 Hz
is higher than impedance corresponding to 1.705 MHz to 80 MHz.
As an example of the circuit configuration of the filter 210, four
inductors and a capacitor are connected as shown in FIG. 2, thereby
realizing a low pass filter. That is, the low pass filter is
realized by connecting in parallel two sets of inductors, each of
which is obtained by connecting two inductors in series, and by
connecting points between the-two inductors in the respective two
sets of inductors to each other by the use of the capacitor.
However, the filter 210 may be realized in a configuration other
than that described above Furthermore, in the filter 210, all
frequency bands other than the power frequency do not necessarily
correspond to high impedance, as long as impedance corresponding to
at least a communication frequency is higher than impedance
corresponding to a power frequency used for commercial power.
The power circuit 221 supplies power, which is supplied from the
power plug 120 through the filter 210 and the surge absorber 230 on
the first wiring line 231, to the communication circuit 222. In
addition, the communication circuit 222 performs signal conversion
for transmitting to the second wiring line 232 a communication
signal transmitted through the wiring line 233 for Ethernet port,
such as signal conversion for transmitting to the wiring line 233
for Ethernet port a communication signal transmitted through the
second wiring line 232.
The surge absorber 230 is an element whose impedance becomes
extremely small in a high voltage. The surge absorber 230 is
inserted behind the filter 210 and before the wiring lines 241 to
244 for connectors and is electrically connected to the first
wiring line 231. By connecting the surge absorber 230 at the
position, it is possible to prevent the surge absorber 230 from
absorbing a communication signal transmitted on the second wiring
line 232.
As shown in FIG. 4, the power line communication modem 220 includes
the communication circuit 222 and the power circuit 221. The power
circuit 221 has a switching regulator that makes ON/OFF control on
a voltage input from a plug, converts AC components of power to DC
components, and supplies, as converted power, a variety of voltages
(for example, +1.2 V, +3.3 V, or +12 V) to the communication
circuit 222. Specifically, the switching regulator converts AC
components of the power to DC components by using a switching
element. In addition, the power circuit is an example of a power
supply circuit and is not specifically limited to the switching
regulator as-long as power (for example, DC voltage) can be
supplied to the communication circuit.
The communication circuit refers to a circuit capable of
transmitting a communication signal using a modulation method, such
as the OFDM (orthogonal frequency division multiplexing) method,
through the second wiring line corresponding to a power line.
Specifically, the communication circuit is denoted as the
communication circuit 222. The communication circuit 222 includes a
main IC 410, an AFE IC (analog front end IC) 420, a low pass filter
430, a driver IC 440, a coupler 450, a band pass filter 460, an AMP
(AMPLIFIER) IC 470, an ADC (AD conversion) IC 471, a memory 480,
and an Ethernet PHY IC 490. The coupler 450 is connected to the
second wiring line 232.
The Ethernet port (for example, RJ45) 110 is a port for connection
between an Ethernet cable and a communication apparatus (not
shown). The Ethernet PUY IC 490 performs signal conversion with
respect to a signal for Ethernet and a signal for power line
communication. The Ethernet port 110 is connected to the Ethernet
PHY IC 490.
The main IC 410 has a CPU (central processing unit) 411, a PLCMAC
(power line communicationmedia access control layer) block 412, and
a PLCPRY (power line communicationphysical layer) block 413. The
CPU (central processing unit) 411 is mounted with a 32-bit RISC
(reduced instruction set computer) processor. The PLCMAC block 412
manages an MAC layer of a transmitted signal in the power line
communication and serves to control the PLCPHY block 413 or check
whether or not signal data for power line communication is
correct.
The PLCPHY block 413 manages a PHY layer of a transmitted signal in
the power line communication and performs processing on a
transmitted signal and processing on a received signal For example,
with respect to a transmitted signal when a multi-carrier
communication method is used in the power line communication, the
PLCPHY block 413 performs symbol mapping by converting bit data,
which is the transmitted signal, into symbol data, converts serial
data into parallel data, or performs desired frequency-time
transform, such as the inverse fast Fourier transform (IFFT) or the
inverse discrete wavelet transform (IDWT). For example, with
respect to a received signal when a multi-carrier communication
method is used in the power line communication, the PLCPHY block
413 performs symbol mapping by converting bit data, which is the
transmitted signal, into symbol data, converts serial data into
parallel data, or performs desired frequency-time conversion, such
as the inverse fast Fourier transform (IFFT) or the inverse
discrete wavelet transform (IDWT). In addition, the PLC MAC 412 is
connected to the Ethernet PHY IC 490. In addition, the CPU 411 is
connected to the PLCMAC block 412. In addition, the PLCPUY block
413 is connected to the PLCMAC block 412. Moreover, the memory 480
is connected to the CPU 411.
The AFE IC 420 includes a D/A converter (DAC) 421, an A/D converter
(ADC) 422, and a variable amplifier (VGA) 423. The D/A converter
421 is connected to the PLCPHY block 413 and the low pass filter
430. The low pass filter 430 is connected to the driver IC 440. The
D/A converter 422 is connected to the PLCPHY block 413 and the
variable amplifier 423. The VGA 423 is connected to the band pass
filter 460. In addition, the D/A converter 421, the low pass filter
430, and the driver IC 440 form a transmission system that performs
signal processing in which a power line communication signal is fed
to the second wiring line 232. In addition) the A/D converter 422,
the VGA 423, and the band pass filter 460 form a receiving system
that performs signal processing in which the power line
communication signal is received from the second wiring line
232.
The coupler 450 has a coil transformer 451 and a coupling capacitor
452. The coupler 450 serves to superimpose a signal from the
transmission system, as a power line communication signal, on the
second wiring line 232, extracts only a power line communication
signal from the second wiring line 232, and outputs the power line
communication signal to the receiving system. In addition, the
coupler 450 is connected to the driver IC 440 and the band pass
filter 460.
Further, the ADC IC 471 is connected to the PLCPHY block 413 and
the AM IC 470. Moreover, the AMP IC 470 is connected to the coupler
450.
Here, referring to FIGS. 5 and 6, it will be described about a
difference between effects of an unbalanced (asymmetrical between
approach path and return path) filter 502 and a balanced
(symmetrical between approach path and return path) filter 210 with
respect to balancing of lines. In addition, the approach path and
the return path are parallel paths through which AC power can be
freely transmitted. In this case, the second wiring line 232 has a
pair of approach path and return path. Referring to FIG. 5,
reference numeral 505 denotes parasitic capacitance between a power
line 501 and ground, and reference numeral 506 denotes parasitic
capacitance between power connector lines 507a and 507b and ground.
If a circuit subsequent to the unbalanced filter 502 is not
connected, capacitance between wiring lines 501a and 501b, which
form the power line 501, and ground is equal. Accordingly, in this
case, the power line 501 is balanced. In the case in which a
circuit (unbalanced filter 502 and power connectors 503 and 504)
subsequent to the unbalanced filter 502 is connected, assuming that
impedance seen from an A point toward the direction of the
unbalanced filter 502 is Za and impedance seen from a B point
toward the direction of the unbalanced filter 502 is Zb, impedance
between the wiring line 501a and ground becomes parallel impedance
of the power line-to-ground parasitic capacitance 505 and the
impedance Za and impedance between the wiring line 501b and ground
becomes parallel impedance of the power connector line-to-ground
parasitic capacitance 506 and the impedance Zb. As is apparent from
FIG. 5, the circuit seen from the A point is different from the
circuit seen from the B point. Accordingly, the impedance Za and
impedance Zb are different from each other. As a result, a
difference between impedance between the wiring line 501a and
ground and impedance between the wiring line 501 b and ground
occurs, which lowers the balance, wherein LCL (Longitudinal
Conversion Loss) increases. When power line communication is
performed by using power lines whose balance is reduced, a leaking
electromagnetic field increases,
Next, referring to FIG. 6 again, a case in which the balanced
filter 210 is used will be described. In FIG. 6, the same parts as
in FIG. 5 are denoted by the same reference numerals. The
characteristics of the parts denoted by the same reference numerals
are as described above.
The balanced filter 210 has a capacitor Cf, as shown in FIG. 6. Two
inductors Lf are connected to both ends of the capacitor Cf,
respectively. The two inductors Lf have equal characteristic values
(unit: Heny). In addition, values of the two inductors Lf may be
substantially equal to an extent that the balance can be
suppressed. The balanced filter 210 has four inductors Lf. One of
the inductors Lf connected to one end of the capacitor Cf is
connected to the wiring line 501a. One of the inductors Lf
connected to the other end of the capacitor Cf is connected to the
wiring line 501b. In addition, one of the inductors Lf connected to
the one end of the capacitor Cf is connected to one ends of the
power connectors 503 and 504 and power connector line-to-ground
parasitic capacitance 506. The rest one of the inductors Lf
connected to the other end of the capacitor Cf is connected to the
other ends of the power connectors 503 and 504 and power connector
line-to-ground parasitic capacitance 506. That is, in the balanced
filter 210, both ends of the capacitor Cf are connected to the
wiring lines 501a and 501b through the inductors Lf, respectively.
Thus, a filter having the inductors Lf provided at a line in which
a signal is input from the wiring lines 501a and 501b to the
balanced filter 210 is called an inductance input type filter. The
inductors Lf is an example of a passive element and has a
predetermined characteristic value
As described above in FIG. 5, the power line 501 is a balanced line
if the balanced filter 210 is not connected. In the case in which a
circuit (balanced filter 210 and power connectors 503 and 504)
subsequent to the balanced filter 210 is connected, assuming that
impedance seen from an A point toward the direction of the balanced
filter 210 is Za' and impedance seen from a B point toward the
direction of the balanced filter 210 is Zb', impedance between the
wiring line 501a and ground becomes parallel impedance of the power
line to-ground parasitic capacitance 505 and the impedance Za' and
impedance between the wiring line 501b and ground becomes parallel
impedance of the power connector line-to-ground parasitic
capacitance 506 and the impedance Zb'. As is apparent from FIG. 6,
the circuit seen from the A point are equal to the circuit seen
from the B point. Accordingly, the impedance Za' and impedance Zb'
are equal to each other. As a result, even if a circuit subsequent
to the balanced filter 210 is connected, the impedance between the
wiring lines 501a and ground is equal, and thus a balanced line is
maintained.
Further, in the case when the unbalanced filter 502 and the
balanced filter 210 are formed by using the constant K filter
having characteristic impedance of 100 .OMEGA. and a cutoff
frequency of 50 KHz, for example, a gain-frequency characteristic
view is shown in FIG. 7A and an impedance-frequency characteristic
view is shown in FIG. 7B. In the impedance-frequency characteristic
view, it is assumed that a load of 1 .OMEGA. is connected
considering that a power apparatus (not shown) is connected. As is
apparent from FIG. 7B, in both the balanced filter 210 and the
unbalanced filter 502, power is transmitted with low loss in a
commercial power frequency band bat the loss increases in a
shortwave band such that, for example, noises that affect
communication can be electively excluded. However, as shown in FIG.
7B, referring to the impedance characteristic within the shortwave
band, the filter 502 becomes low impedance to serve as a large load
of a power line communication modem, while the filter 210 can be
considered as a very small load so as not to affect communication
performance. This is advantageous in that the communication
performance does not deteriorate, for example, when various
apparatuses are connected to the connectors 101 to 104.
As an example of the circuit configuration of the filter 210, four
inductors and a capacitor are connected as shown in FIG. 2, thereby
realizing a low pass filter. However, the filter 210 may be
realized in other configurations. For example, the filter 210 may
be simply configured to include two inductors, as shown in FIG. 8A.
In addition, when devices connected to the connectors 101 to 104 do
not consume a large amount of power, as shown in FIG. 8B, it is
possible to improve impedance by magnetically coupling the
inductors in FIG. 8A. Alternatively, in order to improve balancing
of lines, the filter 210 may be formed by combination with a common
mode filter (not shown). Further, in the present embodiment, the
constant K filter that can be easily designed has been used.
However, it may be possible to use the Butterworth filter, the
Chebychev filter, the inverse Chebychev filter, or the cascaded
chevyshev filter, for example.
Furthermore, in power line communication using a shortwave band, it
is requested to suppress unnecessary leakage of electric field in
order to prevent interference with respect to other communication
apparatuses (for example, a shortwave receiver, an amateur radio
transceiver, or a wireless apparatus in aircraft or ship) using a
shortwave band. Therefore, although power lines in the vicinity of
outlets in home, in which apparatuses are actually connected, in
the shortwave band may be considered as almost balanced lines, it
is possible to prevent unnecessary leakage of electric field from
increasing without significantly lowering balancing of the power
lines by using a balanced (symmetrical between approach path and
return path) filter in the cable connecting device for power line
communication 100 so as to be connected thereto.
Furthermore, by adopting an inductance input type filter as a
filter used for the cable connecting device for power line
communication 100, the filter serves as high impedance in power
line communication using a shortwave band (for example, 2 to 30 MHz
or 1.7 to 30 MHz) and a load of the filter becomes small (because
reflection is reduced as a current decreases). That is, it is
advantageous in that the communication performance does not
deteriorate. In addition, without being limited to the shortwave
band, that is, in a frequency band of 30 MHz or more, for example,
even in a megahertz frequency band of 1.705 to 80 MHz, the same
effects can be obtained.
Thus, the cable connecting device for power line communication 100
according to the first embodiment of the invention is configured to
include: the first wiring line 231 through which AC power is
capable of being supplied; the second wiring line 232 through which
AC power is capable of being supplied and which is different from
the first wiring line 231; the power plug 120 which is electrically
connected to the first wiring line 231 and the second wiring line
232 and whose wiring lines are capable of being supplied with AC
power; the Ethernet port 110 through which a communication signal
is capable of being input and output; the power line communication
modem 220 that is connected to the Ethernet port 110 and that is
connected to the second wiring line 232 through which a
communication signal is transmitted by using AC power input to the
power plug 120 through the first wiring line 231 between the power
plug 120 and the Ethernet port 110; the filter 210 disposed on the
first wiring line 231 and having high impedance in at least a
communication frequency band rather than a power frequency; and the
connectors 101 to 104 which are electrically connected to the first
wiring line 231 between the filter 210 and the power line
communication modem 220 and to which AC power from the first wiring
line 231 is capable of being supplied. The first wiring line 231 is
connected to the power circuit 221 (refer to FIG. 2) that supplies
power required for operation of the power line communication modem
220. Similar to power supplies of apparatuses connected to the
connectors 101 to 104, even in the power circuit 221 of the power
line communication modem 220, an adverse effect is prevented in the
filter 210 even if reduction of impedance or noise that affects
communication occurs.
Thus, the power circuit 221 and the connectors 101 to 104 are
connected to the power plug 120 through the single filter 210,
since the filter 210 can suppress noises occurring in the power
circuit 221 and prevent communication signals from being input to
electrical equipment (for example, a battery charger) connected to
the connectors 101 to 104. Accordingly, since it is not necessary
to separately prepare a filter for a power circuit and a filter for
electrical equipment connected to the connectors 101 to 104, a
filter can be efficiently used. As a result, duplication of filters
can be prevented. Moreover, the filter can be used as impedance for
the electrical equipment connected to the connectors 101 to
104.
Second Embodiment
Next, in a second embodiment, it will be described about a cable
connecting device for power line communication having a selection
switch capable of switching a function corresponding to an
apparatus that is connected, assuming a case of connecting a power
line communication apparatus to a connector and a case of connected
a non-power line communication apparatus to a connector.
First, the second embodiment will be schematically described with
reference to FIG. 1. Here, only points different from those in the
first embodiment will be described. Connectors 101 to 104 in FIG. 1
cause power to be supplied to a non-power line communication
apparatus, power to be supplied to a power line communication
apparatus, and a communication signal to be input and output. In
addition, a selection switch 130 is a unit that selects whether to
reduce a signal, which does not belong to a power frequency band,
occurring due to an apparatus connected to the connector 101, that
is, a unit that selects whether to cause the signal not belonging
to a power frequency band to pass through the filter 210.
As shown in FIG. 3, in a cable connecting device for power line
communication 300, the same parts as in the cable connecting device
for power line communication 100 shown in FIG. 1 are denoted by the
same reference numerals. The characteristics of the parts denoted
by the same reference numerals are as described above.
The cable connecting device for power line communication 300
includes a selection switch 310 and a first terminal 301 and a
second terminal 302, which are electrically connected to the
connector 101 by means of the selection switch 310, in addition to
the configuration of the cable connecting device for power line
communication 100. Although all reference numerals are not shown
the selection switch 310 corresponding to each of a pair of
recessed connection terminals is provided in each of the connectors
101 to 104, and a first terminal 301 and a second terminal 302 are
prepared for each selection switch 310. That is, in the present
embodiment, eight selection switches 310, eight first terminals
301, and eight second terminals 302 are provided. In addition, the
selection switch 310 is an example of a selector.
The first terminal 301 is a terminal at which each of the
connectors 101 to 104 and the first wiring line 231 are
electrically connected to each other by means of a first connector
line 311 and which is electrically connected to the selection
switch 310 in order to transmit power supplied from the power plug
120 to each of the connectors 101 to 104. A connection point
between each of the first connector lines 311 and the first wiring
line 231 is provided behind a surge absorber 230 and before a power
line communication modem 220 on the first wiring line 231.
Further, the second terminal 302 is a terminal at which each of the
connectors 101 to 104 and the second wiring line 232 are
electrically connected to each other by means of a second connector
line 312 and which performs supply of power from the power plug 120
to each of the connectors 101 to 104 and transmission and reception
of a communication signal to each of the connectors 101 to 104.
Assuming that a side close to the power plug 120 is a `front stage`
and a side close to the power line communication modem 220 is a
`rear stage` on the second wiring line 232, a connection point
between the second connector line 312 and the second wiring line
232 is provided behind a connection point between the first wiring
line 231 and the second wiring line 232 and before the power line
communication modem 220.
As shown in FIG. 3, the filter 210 is inserted between the
connectors 101 to 104 and the power plug 120 when the selection
switch 310 is connected to the first terminals 301, while the
filter 210 is not inserted between the connectors 101 to 104 and
the power plug 120 when the selection switch 310 is connected to
the second terminals 302. Since the selection switch 310 operates
in conjunction with the selection switch 130 (refer to FIG. 1), the
selection switch 310 switches on the basis of switching of the
selection switch 130.
When a power line communication apparatus is connected to the cable
connecting device for power line communication 300, power supply
and input and output of communication signals are realized by
connecting the power plug 120 of the power line communication
apparatus to the connectors 101 to 104. Since high-frequency signal
components are generally used for the communication signals, the
selection switch 310 is connected to the second terminal 302 so
that the communication signals do not pass through the filter
210.
In addition, when a non-power line communication apparatus is
connected to the cable connecting device for power line
communication 300, power supply-is realized by connecting an outlet
of the non-power line communication apparatus to the connector 101
and input and output of a communication signal is realized by
connecting a communication cable, such as a LAN cable, of the
non-power line communication apparatus to the Ethernet port 110 In
the connectors 101 to 104, high-frequency signals other than
electrical signals of commercial power are noises. Accordingly, the
selection switch 310 is connected to the first terminal 301 so that
the noises are removed while passing through the filter 210.
Thus, in the connectors 101 to 104 of the cable connecting device
for power line communication 300 according to the present
embodiment of the invention, the filter 210 is inserted on the
assumption that a power line communication apparatus as well as a
non-power line communication apparatus is connected to the
connectors 101 to 104. As a result, the connectors 101 to 104 are
very useful because the connectors 101 to 104 can also be used for
the power line communication apparatus.
In the second embodiment, the cable connecting device for power
line communication 300 is configured to include the selection
switch 310, which serves to switch connection between the
connectors 101 to 104 and the first wiring line 231 to connection
between the connectors 101 to 104 and the second wiring line 232.
Therefore, the cable connecting device for power line communication
300 according to the second embodiment may be used for both the
power line communication apparatus and the non-power line
communication apparatus
Moreover, in the first and second embodiments described above, the
cable connecting device for power line communication has been
illustrated as an example of the power line communication
apparatus. However, the invention is not specifically limited to
the `cable connecting device for power line communication`. For
example, it is possible to use a modem having an outlet that is a
connector different from a communication connector, such as RJ45,
and a power connector, such as a plug. In addition, the invention
may not necessarily have a communication circuit or may have a
configuration in which power supplied from a plug is output to the
outside by a power circuit.
The invention is useful as a power line communication apparatus and
a connecting device capable of efficiently using a filter.
This application is based upon and claims the benefit of priority
of Japanese Patent Application No. 2006-038319 filed on Feb. 15,
2006, the contents of which are incorporated herein by reference in
its entirety.
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